These peculiar galaxies have a lot to teach us.
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The galaxies in the two compendiums are striking at first glance. From rings and lopsided spirals to connected galaxies like Wild’s Triplet, their shapes veer far from the familiar image of the Milky Way.
The shape of a galaxy can tell astronomers a lot about how it was formed, but deciphering that message is difficult. When Arp started his catalogs, the formation of spiral galaxies was poorly understood.
These catalogs provide compelling targets for future observations that could help solve the mystery of peculiar galaxies’ formation — a mission that Hubble has continued.